Collet wrench

ABSTRACT

A collet wrench adapted to place a predetermined force on a collet threadedly secured in a dental handpiece. The wrench comprises a frame and means on the frame for securing the rotor shaft against rotation. A shaft is rotably mounted in the frame, and has a lower end of non-circular cross-section. The lower end is received in the collet and is adapted to rotate the collet relative to the rotor shaft. A disc having ratchet teeth is keyed to the shaft and a second disc having ratchet teeth is placed on the first mentioned disc and held there by a spring force. Rotation of the second disc causes the rotation of the first disc, and the subsequent rotation of the shaft having the end secured to the collet. After a predetermined force has been applied to the second disc, it will slip relative to the first disc, and accordingly apply a predetermined force to the collet. The pressure of the spring controls the predetermined force.

This invention relates to a collet wrench, and more particularly, to awrench adapted to secure a bur in an air driven dental handpiece.

It is now common practice in the dental art to supply rotative power toa dental handpiece through the use of an air driven rotor or turbine.Extremely high speeds have been attained utilizing pneumatically drivendental handpieces. A major improvement in air driven dental handpieceshas been the provision of a bur-securing collet that is threadedlysecured in the rotor shaft of the air turbine rotor. The collet hascompressible jaws on the lower end and is threadedly secured to therotor shaft at the upper end. A bur is secured in or released from thecollet by threadedly advancing or retracting the collet relative to therotor shaft, which in turn compresses or opens the jaws of the collet.The threaded collet and its method of securing a dental bur in thehandpiece are disclosed in U.S. Pat. No. 3,120,706.

Since the invention of U.S. Pat. No. 3,120,706 was made, variousattempts have been made to improve the wrench assembly for advancing andretracting the collet relative to the rotor shaft. Some of theseimprovements are disclosed in U.S. Pat. Nos. 3,499,223 and 3,325,899,and in U.S. application Ser. No. 476,749, filed June 5, 1974, thedisclosure of which is incorporated by reference herein.

It has now been found that all of the collet wrenches previously knownto the art have had one disadvantage in common. Thus, all of thesewrenches have a knob for rotating the shaft that is received in thecollet, which knob is keyed to the shaft, or otherwise secured, as by apressed fit. It has further been found that when a man rotates thisknob, he will apply, on the average, a given force to the collet tothreadedly secure it in place when a bur has been inserted in thecollet. Likewise, a woman utilizing the same wrench will supply asubstantially lower force to the wrench, and accordingly a substantiallylower locking force on the collet securing the bur. In order to increasethe force that a woman applies to the collet wrench, it is necessary toincrease the diameter of the knob securing the shaft for locking thecollet in place. However, if the knob diameter is increased, a manutilizing the wrench will in turn apply a substantially greater force tothe collet.

Since it is inconvenient to have separate wrenches for men and women,and since both men and women will use the same handpiece and wrench, aproblem has arisen. Thus, if the knob is made too large, a man willapply too great a force to the collet, thereby either stripping thethreads or securing the bur in place with too great a force, making itdifficult to remove the bur. Alternatively, if the knob diamater is toosmall, a woman will not supply sufficient force to the collet, and thebur may become inadvertently loosened and fall out, or will not be heldsecurely in place, thereby resulting in non-concentric rotation of thebur during use.

All of the problems of proper force on the collet are eliminated byutilizing the collet wrench of this invention. Thus, the knob is madesufficiently large to enable either a man or a woman to apply thecorrect force for securing the bur in place, while at the same time, notapplying too great a force to damage the collet or lock the bur in placeto the extent that it can not easily be removed. The collet wrench ofthis invention includes a slip mechanism whereby once the proper forcehas been applied, no greater force can be applied to the collet.

Although the wrench of this invention was specifically developed for useas a collet wrench, it has been found that it can be used in many otherindustrial applications. Thus, utilizing the teachings of thisinvention, a torque wrench can be made which can be used in any areawhere the prior art torque wrenches have been used. In the prior arttorque wrenches the driving handle is keyed to the wrench shaft. A gaugeis formed on the handle to indicate the amount of torque that is beingapplied. Utilizing the wrench of this invention, the amount of torquethat will be applied can be preset by the judicious selection of aspring, and accordingly, the preset torque will always be applied. Thereis no need to refer to gauges, since it will be known by the user thatthe same predetermined torque will always be applied.

It is accordingly an object of this invention to provide a novel colletwrench for use on an air driven dental handpiece.

It is another object of this invention to provide a novel torque wrench.

These and other objects of this invention are accomplished by providinga wrench comprising a shaft, said shaft having one end configured to bereceived in a threaded, rotatable securing device, the other end of saidshaft having a disc secured thereto, said disc having teeth formed inthe upper surface thereof, a second disc overlying said first disc, andbeing rotatably mounted on said shaft, said second disc having teethwhich are complementary with the teeth in said first disc, spring meansurging said second disc into contact with said first disc, and means forrotating said second disc relative to said first disc.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 is an exploded side elevational view showing the collet wrench ofthis invention and a handpiece on which the collet wrench may be used;

FIG. 2 is a perspective view showing the collet wrench of this inventionas placed on the dental handpiece of FIG. 1;

FIG. 3 is a sectional view showing the collet wrench of this inventionas secured in place;

FIG. 4 is an exploded perspective view showing the elements forming theupper part of the collet wrench of this invention;

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 3;

FIG. 6 is a sectional view taken along the line 6--6 of FIG. 3;

FIG. 7 is a sectional view taken along the line 7--7 of FIG. 3;

FIG. 8 is an enlarged sectional view of the upper portion of the colletwrench of FIG. 3; and

FIG. 9 is an enlarged sectional view showing the meshing of the teeth ofthe two discs of the wrench of this invention.

Referring now in greater detail to the various figures of the drawingswherein like reference character refer to like parts, a collet wrenchembodying the present invention is generally shown at 20 in FIG. 1. Anair driven dental handpiece on which the wrench 20 may be used is alsogenerally shown at 22 in FIG. 1.

The dental handpiece 22 includes a hollow handle 24 having an angledneck 26 and a turbine housing 28 mounted perpendicularly to neck 26. Anadaptor nut 30 is threadedly secured on handle 24 and a connector sleeve32 is threadedly secured on adaptor nut 30. The connector sleeve 32 isused for connecting external sources of air 34, light transmittingfibers 36 and water 38 with the handpiece. A collar 40 is slideablymounted on neck 26, and supports water spray tubes 42. An internal fiberoptic light system terminates in tubes 44.

Referring to FIG. 3, it is seen that turbine housing 28 includes aturbine cartridge 46. Turbine cartridge 46 comprises upper ball bearing48, lower ball bearing 50, a rotor shaft 52, a hub 54 keyed to the rotorshaft and blades 56 projecting from hub 54. A hollow collet 58 isthreadedly secured within rotor shaft 52 by threads 60.

The rotor shaft includes an inwardly tapering wall 62 at its bottom.Likewise, the exterior wall of collet 58 is inwardly tapering, as shownat 64 in FIG. 3. The collet includes a pair of diametrically opposedslots (one shown in phantom at 66 in FIG. 3), which slots divide thecollet into a pair of jaws. The top of collet 58 is provided with a bore68 of non-circular cross-section. In the embodiment of the inventionshown, the bore has a hexagonal cross-section. As will be explainedhereinafter, the rotation of the collet 58 in rotor shaft 52 causes thecompression of the jaws of the collet, thereby securing the shaft ofdental bur 70 within the collet.

Turbine housing 28 is provided with a threadedly secured upper end cap72 and a threadedly secured lower end cap 74. As seen in FIG. 3, theouter races of ball bearings 48 and 50 are contacted by the innersurfaces of the end caps 72 and 74. However, each end cap is providedwith an internal recess whereby the end caps will not be contacted bythe inner races of the ball bearings. Accordingly, the rotor shaft 52,which is keyed to the inner races, is freely rotatable along with theinner races between the end caps 72 and 74.

As is apparent from FIG. 3, the turbine cartridge 46 comprises the rotorshaft, the ball bearings, the collet and the rotor. This cartridge isremovable as a unit from the turbine housing 28 by the removal of theend caps 72 and 74, whereby the turbine cartridge may be slid from theturbine housing. The air for rotating the rotor blades 56, and in turn,the rotor shaft 52 with its secured collet 58, is furnished by airconduit 76. The exhaust air leaves through ports 78 in turbine housing28, and then back through neck 26 and handle 24.

To the extent described, the dental handpiece 22, including the elementsof turbine housing 28, is the same as that disclosed in U.S. applicationSer. No. 476,759, filed June 5, 1974, the disclosure of which has beenincorporated by reference herein. This specific handpiece has been shownby way of example. The collet wrench of this invention is adapted foruse on any air driven dental handpiece having a threaded collet of thetype described, such as those shown in the aforementioned United StatesPatents. The collet wrench 20 forming this invention will now bedescribed.

Wrench 20 includes a frame 80 having an upper leg 82, a vertical leg 84and a lower leg 86. A pair of flanges 88 project from leg 84 (FIGS. 2and 6). Lower leg 86 includes an inwardly extending cut 90 that has apair of straight sides 92 (FIG. 7). As seen in FIG. 7, the rotor shaft52 has a square cross section at its lower end, and the straight sides92 act as a wrench to grasp the rotor shaft at said lower end when thedevice 20 is placed on the turbine housing 28. As will be explainedhereinafter, the straight sides 92 prevent rotation of the rotor shaft52 when the collet 58 is being moved relative to the rotor shaft.

A collet advancing shaft 94 is rotatably mounted in bushing 96, which isin turn secured in upper leg 82 of frame 80 (FIG. 3). As will beexplained hereinafter, shaft 94 is also vertically reciprocable inbushing 96. A split ring 98 is secured on shaft 94 in an annular groove100 in the shaft. A compression spring 102 is positioned around shaft 94and bears against the upper side of ring 98 and the lower side ofbushing 96. The bottom of shaft 94 has a reduced head 104 ofnon-circular cross-section. The cross-section of head 104 is the same asthe upper bore 68 of collet 58, and is slightly smaller in size than thebore of the collet so that it can be inserted in said bore.

A disc 106 is secured on shaft 94 adjacent the top thereof. The top ofshaft 94 is provided with a plurality of spaced vertical slots 108. Aclutch plate 110 having a central opening 112 is secured on shaft 94over disc 106. The opening 112 is approximately the same diameter as thediameter of the shaft 94, and the securement of the clutch plate 110occurs by the frictional engagement of the slotted top 108 in opening112. As seen in FIG. 4, clutch plate 110 includes a plurality of teeth114 which extend around its entire outer surface.

Referring still to FIG. 4, a drive plate 116 having a central opening118 is provided. Drive plate 116 includes a plurality of teeth 120 whichextend around opening 118. The perimeter of drive plate 116 includes aplurality of equally spaced slots 122.

In the assembly of the wrench 20, as best seen in FIG. 8, the driveplate 116 is placed over the top of shaft 94, with the teeth 120 engagedin the teeth 114. As further seen in FIG. 8, since the opening 118 indrive plate 116 is substantially larger than the diameter of shaft 94,the drive plate 116 can rotate relative to the shaft 94. As seen in FIG.9, teeth 114 and teeth 120 each include a relatively long gradualinclined surface 124 and a relatively short, sharply inclined surface126. The angle of surface 124 is substantially smaller than the angle ofsurface 126. The teeth 114 and 120 extend in the same direction and atidentical angles. Thus, in the assembled condition of the wrench, theseteeth are enmeshed, as seen in FIGS. 3, 8 and 9.

Referring again to FIG. 4, it is seen that the wrench 20 furtherincludes a hollow drive cylinder 128 having equally spaced legs 130projecting downwardly at the bottom thereof. The upper portion of theouter surface of the drive cylinder 128 includes a plurality of slots132. Referring to FIGS. 3 and 8, it is seen that in the assembledcondition of wrench 20, cylinder 128 is positioned above plates 110 and116, and legs 130 are engaged in slots 122 of plate 116 (see also FIG.5).

A compression spring 134 is placed within cylinder 128, with the lowerend of the spring abutting teeth 120 on drive plate 116. A hollowcylindrical knob 136 is placed over cylinder 128, and is held in placeby the frictional engagement of the slotted portion 132 of cylinder 128against the interior wall of knob 136. As seen in FIG. 2, 136 has aknurled outer surface to aid in grasping the same. As seen in FIG. 3,knob 136 includes a lower annular groove, and a retainer ring 140 ismounted in this groove. In the assembled condition of the wrench, thespring 134 tends to push disc 106 downwardly, and the disc in turn bearsagainst retainer ring 140.

Referring to FIG. 3, the wrench 20 is used by grasping knob 136 andlifting it vertically upward to the position shown at 136'. This in turnwill lift the shaft 94 vertically to the extent that the lower end 104of the shaft is spaced a distance from leg 86 of frame 80 which isgreater than the height of turbine housing 28. The lifting of the knob136 is against the urging of spring 102.

With the knob 136 so lifted, and the consequent lifting of shaft 94, theframe 80 can be placed over turbine housing 28, with the bottom of rotorshaft 52 being received in slot 90 (FIG. 7). It should be kept in mindthat the rotor shaft 52 is freely rotatable, and thus the insertion ofthe rotor shaft in the slot is easily accomplished. With the rotor shaftso engaged, the knob 136 is released. Spring 102, acting against splitring 98, then forces the shaft 94 downwardly so that the end 104 of theshaft is received in hexagonal bore 68 of the collet. The shaft 94 isfreely rotatable, and accordingly it can easily be engaged in the top ofthe collet.

As explained in the aforementioned United States Patents andaforementioned U.S. application Ser. No. 476,749, when the collet 58 isin its upper position, the jaws formed at slots 66 are open. A dentalbur 70 can then be inserted between the jaws and subsequently secured inplace by the threaded advancement of the collet downwardly relative torotor shaft 52. Thus, when the collet is rotated relative to the rotorshaft, at threads 60, the tapered jaws 64 are compressed by the taperedwall 62 of the rotor shaft 52.

In order to rotate the collet relative to the rotor shaft, the rotorshaft must be maintained in a stationary condition. This is accomplishedby the engagement of the outer surface of the rotor shaft with the jawsformed by the slot 90 of leg 86. The engagement of the flanges 88 (FIGS.6 and 7) with the turbine housing 28 prevents any substantial rotationof the frame once it has been secured in place, and accordingly, therecan be no substantial rotation of the rotor shaft once it is engaged inthe jaws of the lower leg 86. The shaft 94 is then rotated through theknob 136 to threadedly advance the collet downwardly in the rotor shaftin order to secure the bur 70 in place.

The rotating mechanism for the shaft 94 will now be explained. Spring134 engages the teeth 120 of plate 116 with the teeth 114 of plate 110.Accordingly, when the knob 136 is rotated, there will be a consequentrotation of shaft 94, since the plate 110 is keyed to the shaft. This inturn will rotate the collet along threads 60. The rotor shaft 52 ismaintained in a stationary condition by the jaws of lower leg 86.

Eventually, the collet will tightly secure the dental bur 70 in place.When this occurs, continued rotation of the knob 136 will cause theplate 116 to rotate relative to the plate 110. Thus, referring to FIG.9, it is seen that the inclined portion of the teeth 120 can slide overthe inclined portion of the teeth 114. Until there is any resistance tothe rotation of the shaft, which occurs when the collet is tightlysecured in place, the spring 134 maintains the engagement between theteeth of plate 116 and plate 110. However, once the collet is secured inits predetermined maximum lower position, the continued rotation of theknob 136 overcomes the the force of the spring 134, and accordingly theteeth of the upper plate 116 will ride over the teeth of the lower plate110. The amount of force needed to accomplish this riding over featureis directly dependent on the strength of the spring 134. Thus, thelighter the force of the spring, the sooner the riding over will occur.By the judicious selection of the spring force, the amount of tightnesson the collet can be regulated.

When the collet is tightened on the dental bur 70, the knob 136 isrotated in a clock wise direction, as viewed in FIGS. 2 and 3. When itis desired to remove the bur, the collet 58 must be raised relative tothe rotor shaft 52, so that the jaws are opened. In order to accomplishthis, the knob 136 is rotated in a counter-clock wise direction. Whenthis occurs, the spring 134 keeps the teeth of the plates 116 and 110firmly engaged. Furthermore, because of the sharper angle 126 of theteeth, the counter-clock wise rotation of the knob will not permit theupper teeth to ride over the lower teeth. Accordingly, the collet willalways be rotated whenever the knob 136 is rotated in a counter-clockwise direction. This causes the collet to be raised relative to therotor shaft, causes the jaws of the collet to open, and permits thedental bur 70 to drop from the collet.

The transmission of the rotational power of the knob 136 to the shaftshould be readily apparent from FIG. 3. Thus, the knob is keyed to thedrive cylinder 128 by a pressed fit. When the knob is rotated, thecylinder 128 will likewise be rotated. The cylinder has the lower legs130 engaged in the slots 122 of the plate 116. Accordingly, when thecylinder is rotated by the knob 136, the plate 116 will likewise berotated.

Since the spring 134 maintains contact between the teeth of plate 116and the plate 110, when the plate 116 is first rotated, the plate 110will likewise be rotated. Since the plate 110 is keyed to the shaft 94,the rotation of the plate 110 in turn rotates the shaft 94.

As pointed out above, through the judicious selection of spring sizes,the maximum force applied to the collet can easily be set. Utilizing theprior art wrenches, when a knob for the wrench had a diameter ofapproximately 1/4 inch, it was found that a woman utilizing thehandpiece would apply a torque of approximately 1/2 pound inch. A manutilizing the same wrench would apply a torque to the collet of 1 1/2pound inches. It has now been determined that the maximum effectivetorque to be applied to the collet is 1 pound inch. The knob is made ofa diameter which is sufficiently large for a woman to use to obtain thistorque. By way of example, the outer diameter of the knob 136 is 1/2inch. By way of further non-limiting example, in order to obtain the 1pound inch of torque, the spring 134 has a rate of 67 pounds per inch, afree length of 0.380 inch and a wire diameter of 0.040 inch. The load atwhich the upper plate 116 slips relative to the lower plate 110 is 10pounds, and the length of the spring at this load is 0.230 inch.

The foregoing ratings are solely by way of example. Obviously, theseparameters can be varied at will in order to obtain the desired presettorque. It is thus seen that the wrench of this invention can readily beused on any air driven dental handpiece wherein the collet is threadedlysecured to the rotor shaft. Any mechanism can be used for preventingrotation of the rotor shaft, such as the slotted leg 86 shown, or themechanism shown in aforementioned U.S. application Ser. No. 476,749. Ifit is desired to reduce the overall height of the wrench, the bushing 96(FIG. 3) can be inverted so that it is placed below the upper leg 82.

Although the invention has been particularly described with reference toa collet wrench for a dental handpiece, it should be understood that theteachings of this invention can be used to make a torque wrench for usewhere any of the prior art torque wrenches have been used. Thus, a leverarm can extend from the knob 136 in order to utilize the wrench forsupplying extremely large torques in industrial applications. Instead ofhaving the lower head 104, any of the socket heads used in prior arttorque wrenches can be used. Likewise, when the wrench is used as anindustrial torque wrench, it will be unnecessary to have the frame 80.The wrench can be constructed, through the judicious selection of spring134, to apply a predetermined torque of substantially any magnitude.

A user of the wrench of this invention can readily determine when theproper torque has been applied since the knob will vibrate when plate116 slides relative to plate 110, and in addition, there will be adistinct clicking sound by the dropping of the teeth in place. The forceof spring 134 is sufficient to permit the loosening of any threadedmechanism which has been tightened by the wrench.

Without further elaboration, the foregoing will so fully illustrate ourinvention that others may, by applying current or future knowledge,readily adapt the same for use under various conditions of service.

What is claimed as the invention is:
 1. A wrench adapted to be hand-heldcomprising a shaft, said shaft having one end configured to be receivedin a threaded, rotatable securing device, said end being adapted tocause the rotating of said securing device when said end is rotated, theother end of said shaft having a first disc secured thereto, said firstdisc having teeth formed in the upper surface thereof, a second discoverlying said first disc, and being rotatable relative to said shaft,said second disc having teeth which are complementary with the teeth insaid first disc on the under surface thereof, spring means urging saidsecond disc into contact with said first disc, and means for rotatingsaid second disc, said rotating means comprising a cylinder, saidcylinder having a plurality of legs projecting downwardly therefrom,said legs being engaged in slots in said second disc, said spring meanshaving a force sufficient to cause the rotation of said first disc whensaid second disc is rotated, and said spring means permitting rotationof said second disc relative to said first disc when a predeterminedrotational force has been applied to said securing device.
 2. The wrenchof claim 1 wherein said rotating means further comprise a knob, saidknob being secured on said cylinder.
 3. The wrench of claim 1 whereinsaid teeth on said first disc and on said second disc have two inclinedsurfaces, one of said surfaces having a smaller angle than the other ofsaid surfaces, said second disc being adapted to rotate relative to saidfirst disc by the disengagement and reingagement of said teeth when saidsecond disc is rotated in a first direction which causes the sliding ofsaid second disc relative to said first disc along said smaller anglesurface.
 4. The wrench of claim 3 wherein said second disc will rotatesaid first disc when said second disc is rotated in a direction oppositethat which causes the sliding of said second disc relative to said firstdisc, said rotating in said opposite direction causing the engagement ofsaid teeth at said larger angle surfaces.
 5. The wrench of claim 1 andfurther including a frame, said shaft being rotatable in said frame,said frame having means thereon for preventing rotation of a rotatableelement in which said securing device is threadedly secured.
 6. A wrenchadapted to be hand-held comprising a frame, said frame having meansthereon for preventing rotation of a rotatable member, a shaft rotatablysecured in said frame, said shaft having one end configured to bereceived in a threaded rotatable securing device, said securing devicebeing threadedly secured on said rotatable member, said end beingadapted to cause the rotation of said securing device when said end isrotated, the other end of said shaft having a first disc securedthereto, a second disc overlying said first disc, and being rotatablerelative to said shaft, said second disc being urged into contact withsaid first disc by spring means, means on the abutting surfaces of saiddiscs to cause the interlocking of said discs whereby the rotation ofthe second disc will cause the rotation of said first disc, and meansfor rotating said second disc, said rotating means comprising acylinder, said cylinder having a plurality of legs projecting downwardlytherefrom, said legs being engaged in slots in said second disc, saidspring means having a force sufficient to cause the rotation of saidfirst disc when said second disc is rotated, and said spring meanspermitting rotation of said second disc when a predetermined rotationalforce has been applied to said securing device.
 7. The wrench of claim 6wherein said frame includes a vertical leg and an upper horizontal legprojecting therefrom, said shaft being rotatably mounted in said upperhorizontal leg.
 8. The wrench of claim 7 wherein said frame furtherincludes a lower horizontal leg, said rotation preventing meanscomprising a slot in said lower horizontal leg, said slot having a pairof jaws configured to grasp flattened surfaces on said rotatable memberto prevent rotation of said rotatable member.
 9. The wrench of claim 6wherein said shaft is also vertically reciprocable in said frame, andsecond spring means urging said shaft downwardly relative to said frame.10. The wrench of claim 6 wherein said engageable means on said discscomprise complementary teeth formed in the upper and lower surfaces ofsaid first and second discs, respectively.
 11. The wrench of claim 6wherein said rotating means further comprise a knob, said knob beingsecured on said cylinder.
 12. The wrench of claim 10 wherein said teethon said disc and on said second disc have two inclined surfaces, one ofsaid surfaces having a smaller angle than the other of said surfaces,said second disc being adapted to rotate relative to said first disc bythe disengagement and reingagement of said teeth when said second discis rotated in a first direction which causes the sliding of said seconddisc relative to said first disc along said smaller angle surface. 13.The wrench of claim 12 wherein said second disc will rotate said firstdisc when said second disc is rotated in a direction opposite that whichcauses the sliding of said second disc relative to said first disc, saidrotating in said opposite direction causing the engagement of said teethat said larger angle surfaces.